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| Titel |
The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days |
| VerfasserIn |
B. O. Ogunsua, J. A. Laoye, I. A. Fuwape, A. B. Rabiu |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 21, no. 1 ; Nr. 21, no. 1 (2014-01-20), S.127-142 |
| Datensatznummer |
250120879
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| Publikation (Nr.) |
 copernicus.org/npg-21-127-2014.pdf |
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| Zusammenfassung |
| The deterministic chaotic behavior and dynamical complexity of the space
plasma dynamical system over Nigeria are analyzed in this study and
characterized. The study was carried out using GPS (Global Positioning System)
TEC (Total Electron Content) time
series, measured in the year 2011 at three GPS receiver stations within
Nigeria, which lies within the equatorial ionization anomaly region. The TEC
time series for the five quietest and five most disturbed days of each month
of the year were selected for the study. The nonlinear aspect of the TEC time
series was obtained by detrending the data. The detrended TEC time series
were subjected to various analyses for phase space reconstruction and to
obtain the values of chaotic quantifiers like Lyapunov exponents, correlation
dimension and also Tsallis entropy for the measurement of dynamical
complexity. The observations made show positive Lyapunov exponents (LE) for
both quiet and disturbed days, which indicates chaoticity, and for different
days the chaoticity of the ionosphere exhibits no definite pattern for either
quiet or disturbed days. However, values of LE were lower for the storm
period compared with its nearest relative quiet periods for all the stations.
The monthly averages of LE and entropy also show no definite pattern for the
month of the year. The values of the correlation dimension computed range
from 2.8 to 3.5, with the lowest values recorded at the storm period of
October 2011. The surrogate data test shows a significance of difference
greater than 2 for all the quantifiers. The entropy values remain relatively
close, with slight changes in these values during storm periods. The values
of Tsallis entropy show similar variation patterns to those of Lyapunov
exponents, with a lot of agreement in their comparison, with all computed
values of Lyapunov exponents correlating with values of Tsallis entropy
within the range of 0.79 to 0.81. These results show that both quantifiers
can be used together as indices in the study of the variation of the
dynamical complexity of the ionosphere. The results also show a strong play
between determinism and stochasticity. The behavior of the ionosphere during
these storm and quiet periods for the seasons of the year are discussed based
on the results obtained from the chaotic quantifiers. |
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